The US mission in Podgorica, the capital of Montenegro, has urged people to avoid the area following a grenade attack on the diplomatic premises by an unknown assailant, who subsequently used a second device to commit suicide.

The attack happened around 00:30 local time Thursday, when an “unknown person” threw an “explosive device” from the street into the US embassy compound, the government of Montenegro announced on Twitter. Authorities believe that the projectile thrown was a hand grenade. Immediately afterward the assailant “committed suicide with an explosive device,” the statement added.

Police have started an investigation and are now looking into possible motives for the attack. Authorities swiftly blocked Revolution Boulevard where the country’s National Security Agency and the US embassy are located. Further details of the incident are yet unclear.

At 00:30, in front of the @USEmbassyMNE building in #Podgorica, #Montenegro an unknown person committed suicide with an explosive device. Immediately before, that person threw an explosive device from the intersection near the Sport Center into the US Embassy compound. (1 of 2)

The US embassy has meanwhile issued a warning urging people to avoid the area. “The US embassy in Podgorica advises US citizens there is an active security situation at the US embassy in Podgorica,” the US embassy in Montenegro said. “Avoid the embassy until further notice.”

The diplomatic mission cancelled all visa services scheduled for Thursday, and said that services for American citizens will be available “on an emergency basis.”

American diplomatic missions across the world are well used to attacks from belligerent locals who disagree with US foreign policy. The most deadly attacks, however, have been carried out by terrorists.

.@USEmbassyMNE confirms there was a small explosion near the U.S. Embassy compound at approximately midnight local time on February 22. The Embassy is currently conducting an internal review to confirm the safety of all staff.

The first major public discontent against US embassies abroad was in Iran, where 52 American citizens, including foreign service agents, were held hostage for 444 days after a group of Iranian students took over the US embassy in Tehran on November 4 1979. A few weeks later, on November 21 1979, an angry mob destroyed the US embassy in Pakistan, burning it to the ground and killing two US security officers in the process over allegations that the United States was involved in the Grand Mosque seizure in Mecca. The same news reports drove a crowd in Libya to attack and destroy the US embassy in Tripoli.

The US embassy in Beirut, Lebanon, has also seen its share of anti-American action, notably in the 1980s at the height of the Lebanese Civil War. On April 18 1983, a jihadist detonated a car bomb outside the US mission killing 63 people, including 17 Americans. On September 20 1984, the Hezbollah militant group carried out a suicide car bombing targeting the US embassy annex in east Beirut, killing 24 people.

The biggest tragedy, however, struck the US missions on August 7 1998, when Al-Qaeda simultaneously attacked with truck bombs in Nairobi, Kenya and Dar es Salaam, Tanzania, killing 224 people.

The most recent major attack against a US diplomatic mission happened on September 11 2012, in Benghazi, Libya. The US ambassador to Libya, Christopher Stevens, and three other Americans were killed during the attack.